Influence of HRT reduction on pilot scale flat sheet submerged membrane bioreactor (sMBR) performances for Oil&Gas wastewater treatment

This study focuses on the utilization of a pilot scale flat sheet submerged ceramic membrane bioreactor to treat Oil&Gas produced water in order to be compliant with future discharge regulations as well as compact and cost competitive versus other existing treatment technologies. Results revealed that, after a microbial acclimation period, it has been possible to run the pilot continuously for several months without encountering critical filtration problems at higher sustainable flux than 10-15 L h(-1) m(-2), permitting to reduce the hydraulic retention time from 45 h down to 11 h. The sustainable flux for these test conditions appeared to be 30 L h(-1) m(-2), corresponding to an HRT of 15 h. Moreover, an ORL of 2.5 kgCOD.m(-3).d(-1), a F/M of 0.2 kgCOD.kgTSS(-1).d(-1) and a SRT of 17 d were retained as optimal operational conditions. The membrane bioreactor permitted to efficiently remove: heavy metals (from 29 to 97%); phenols (up to 100%); BTEX (up to 100%), PAHs (up to 100%) and total organic carbon (96-98%). A specialization of the community was observed and some bacterial species became preponderant even after a microbial perturbation. Finally, toxicity tests revealed a complete absence of toxicity for the reactor outlet.